Pen



FIG. 1 is a front view of a pen showing my new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is an exploded perspective view thereof.

The broken lines illustrate portions of the pen that form no part of the claimed design. 

CLAIM The ornamental design for a pen, as shown and described. 